Prior Art
This invention relates to headless rivets and more particularly to headless rivets having superior strength.
The headless rivet of the present invention is an improvement over the autolocking self-piercing rivet disclosed in abandoned application Ser. No. 906,479 filed May 17, 1978 in that it provides for a riveted fastening of sheet materials wherein the ends of the rivet are flush with surfaces of the fastening materials. Further, the present invention is an improvement over U.S. Pat. No. 4,130,922 due to the added shoulder, ridges and neck portions which provide additional holding strength to the rivet for each sheet of material joined thereby.
Headless riveting itself is not new, as indicated by U.S. Pat. Nos. 3,130,489 and 3,729,804. In the prior art, the lower of the pieces being fastened together must be prepunched to provide an opening for the fastening element and in no case is the fastening means flush with the surfaces of the finished work.
Other patents relating to conventional headless rivets include U.S. Pat. Nos. 412,243; 2,375,116; and 2,463,185. The present invention provides a headless rivet that has an improved strength and locking capabilities over conventional rivets.
The present headless rivet comprises flat ends, shank portions adjacent the flat ends, a shoulder interposed between said shank portions, and curved neck portions extending from said shoulder to said shank portions, the curved neck portions preferably having a predetermined radius determined according to the height of the rivet. The shoulder provides a double lock of the material being joined, which material flows on each side of the shoulder locking the material of each sheet of materials on both edges. That is, each separate sheet of material being joined by the present rivet is respectively held in place by the rivet's adjacent undercut (formed by the curved neck portion). Thus the shank portions and shoulder provide individual locking means for each separate sheet of the material.
Another embodiment of the present invention involves a headless rivet having flat ends shank portions adjacent the flat ends, a shoulder interposed between the shank portions, and a ridge interposed between said shoulder and shank portion with neck portions extending from said shoulder to said ridge and the shank portions with the neck portions having a predetermined radius according to the height of the rivet. This embodiment provides additional strength and locking capablity of the rivet to each sheet of material to be riveted.